Bathroom insulation

Discussion in 'Builders' Talk' started by gingertimmins, Dec 25, 2017.

  1. gingertimmins

    gingertimmins Member

    hi everyone, merry xmas and all that. Not sure if this is the right forum but it seems like the most sensible place to post.

    My situation is that I've just bought a house with a downstairs bathroom, built C1900, and the room is very cold and condensates like crazy. My guess is that it isn't well insulated as it's in the extension.
    It's a typical 2 up 2 down Victorian terraced house with downstairs bathroom in an extension.
    In another thread I asked about plumbing in a bath but now I'm considering insulating the space.
    It's a small area so creating a cavity isn't really an option.
    At the moment all I can see is tiles from floor to ceiling and I guess basic plastering behind.
    My question is would a decent insulating plasterboard straight onto the brick (or whatever is behind the tiles) make a difference.
    I'm hoping that insulating the walls with plasterboard and stuffing some insulation in the pitch roof would at least make it a bit warmer and maybe tame the moisture.

    Any thoughts?

  2. gingertimmins

    gingertimmins Member

    Also... any suggestions on thickness, brands etc.
    Was also lokking to build a really basic floating floor but upon reflection if I could lay some of this plasterboard on the floor and lay tiles on top then I'd be a happy man!
  3. Bob Rathbone

    Bob Rathbone Well-Known Member

    Batten the walls at 600mm centres with 25 X 50 tantalised tiling lath, fit 25mm thick insulation between the battens and a PVC sheet vapour barrier over. Plasterboard with 1200 x 2800 x 12mm board and finish to suit. No need to remove the old plaster unless it is really unstable, use good fixings as the batten will be your fixings for radiators, shelves and towel rails.
  4. Mr Rusty

    Mr Rusty Well-Known Member

    You can get insulated plasterboard in various thicknesses and with various types of insulation - both polystyrene and PIR. Choose a high performance PIR backed board, with a built in vapour barrier and D&D it straight to the bare brick. Definitely remove all the old plaster because you'll gain anything from 10-30mm so won't lose as much when you insulate. e.g.

    how to vid.
    Deleted member 33931 likes this.
  5. Jord86

    Jord86 Well-Known Member

    What's the dimensions of the room, and do you have any photographs please Chris?
  6. gingertimmins

    gingertimmins Member

    Currently driving home from the parents house. Should be able to provide measurements and photos in a couple of hours.
    Anything in particular I should photograph?

    Off the top of me 'ead I'd say the bathroom is 2000mm x 2300mm.
    No idea about ceiling height but it's an angled ceiling
  7. Jord86

    Jord86 Well-Known Member

    Not a bad size then, I envisaged something half the size. I've done my own bathroom out this year, same scenario as yours. Personally I'd gut the lot, hack off the old plaster, drop the ceiling, pull up the floor, the lot. Now this isn't the cheapest way, but it gives the best result. I also have a vaulted ceiling, rakes up about 450mm then levels off, I stuffed every space with 50mm celotex/kingspan insulation, don't use rockwool as it's a waste of time, you'd need tons of it to make a real difference. Whilst the ceiling is down i would fit a ceiling mounted extractor fan. Board the ceiling with foil backed plasterboard, this will act as your vapour barrier and help to control condensation a little better.

    Batten your walls with minimum 25x50mm timber at 400mm centres, I used 50x50 to get more celotex insulation between, fix timber in between the battens in advance to take any cabinets, heavy mirrors etc,fix a vapour barrier stapled to the battens all the way around your room then board with either green moisture resistant plasterboard, or Hardibacker board. Up to you if you tile floor to ceiling, or half tile, or just where the bath and shower is.

    I'm guessing floor is solid, being an extension it should have insulation in it anyway, however if it's suspended I.e. timber, then fit 50mm celotex between joists and board with your choice, though I'd go with a tongue and groove sheet material, especially if you're going to tile on top.

    My bathroom is 1st floor, solid wall terraced house 120year old, with the rear facing the sea, so the cold,wind and rain batters that side of the building, since I've done it out, it's the warmest room in the house without turning any rads on. Was a hell of a lot of work at the time, but really worth it long term, if only to add value to the house.
    KIAB likes this.
  8. gingertimmins

    gingertimmins Member

    IMG_2547.JPG IMG_2548.JPG IMG_2549.JPG Ok having just measured it it is 175x190cm so a bit smaller than estimated.
    Ceiling height is 197 at its lowest and 225 at its max height.
    Next to the bathroom is a small corridor leading to the back garden and the angled ceiling is much higher so it looks as though the bathroom ceiling has been dropped and hopefully insulated.

    Here's a photo or two. Not sure how useful they are as the room is too small to get a decent angle!
  9. Jord86

    Jord86 Well-Known Member

    It's a typical sized small bathroom, a standard 1700 baths length by roughly a baths length, it really depends how far you wish to go with this, as you won't be able to do any worthwhile decent insulating with the current suite installed unfortunately.
  10. gingertimmins

    gingertimmins Member

    Well the whole point of this project is to get rid of the shower and install a bath so I'm thinking to go the whole hog, rip it out and start again. I guess the question is whether I will get noticeable results without sacrificing more than a few cm of internal space.
  11. Jord86

    Jord86 Well-Known Member

    I undoubtedly have in mine, but my room dimensions were 3m x 2.7m, reduced now by 150mm/6" each way, so I had plenty of space to do so, but even if you used 25mm celotex in the walls it would still make a decent difference to the heat loss and condensation. Is your ceiling timber cladding or pvc?
  12. gingertimmins

    gingertimmins Member

    Great, I think I'm going to go for it.
    The ceiling is painted T&G
  13. Jord86

    Jord86 Well-Known Member

    The benefits of short term grief and stress are far outweighed by the long term gain. It's a gamble exactly how much work is involved until you strip everything out. When it's a shell, can take the opportunity to upgrade your lights (spots perhaps), install a good extractor fan in the ceiling, insulate every gap you can see with expanding foam, may be lucky and gain a bit more space in the ceiling once you've removed t+g, as it may be counter battened. Just make sure you leave the toilet in until the last possible second if it's your only bathroom.
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  14. gingertimmins

    gingertimmins Member

    I'm taking a week off and my brother in law is visiting to help. He's a builder but we live in different cities so it's hard to get advice from him. My point is that it shouldn't be too stressful (apart from for my missus!)
    Thanks for the advice, I can now start doing some prep work and buying up some materials!
  15. Jord86

    Jord86 Well-Known Member

    Based on my experience, book your missus a week away somewhere, because it's REALLY not worth the extra grief with her being home whilst it's going on, could have cheerfully strangled mine several times throughout. Good luck.
  16. gingertimmins

    gingertimmins Member

    Sorry to upheave this thread again but can anyone recommend the correct screws and plugs for the battening and then the correct screws for attaching the plasterboard to the battens please?
  17. Hi Ginge.

    Yes, adding insulation like this will make the world of difference.

    I'd re-read Rusty's post #4 and save yourself a lot of grief. And get the best possible results.

    Do you have a second loo you can use meanwhile? Good - so simply clear out everything in this one. If you can bear to do so, also SDS chisel everything off the walls right back to bare brick/block - as said above, that will gain you a good inch, and will also ensure you have a good bonding to the actual wall (in case there was any risk of the existing plaster and tiles having 'blown').

    Ok, there are a few threads on here which argue the pros and cons between battening the walls, adding insulation and then over-boading with p'board versus simple D&Ding thermal board straight on to the bare walls. When I did my own single-skin room, I went for battening. The next time I'll go for D&Ding.

    Pros and cons.

    Battening: Pros - gives you battens to screw things on to. Possibly 'easier' in that it's a known construction method - drilling numerous holes in walls, shoving in numerous plastic plugs and then screwing numerous screws in to secure the battens. Cons - that's a LOT of holes going in to your cold wall, and these screws will then all be pretty bludy cold too. If that wall requires a DPM first (say it's a non-cavity wall or single-skin), then that's a LOT of holes going through it. It's a LOT of work. If the only insulation you then add to that wall is in-between the battens, then the plasterboard screwed on top could (almost certainly will) have cold bridging areas where the only insulation is provided by the timber battens - which has numerous screws in it. The solution to this - which is what I did anyway - is to overboard with TLB, but then you are simply adding more thickness to your wall again.

    D&D is an 'unknown' system for many folk, but a quick look at some videos will show you it's a very straight-forward job.

    Pros of D&Ding ThermLamBoard: Maximises space in the room. You can afford to go for a thicker board and gain extra insulation - eg 45mm overall thickness will give superb insul value. No risk of cold spots - it'll ALL be of identical value. Cons - screws/bolts for items will need to pass through all this and in to the wall behind (not really an issue in practice - just use longer screws...)

    If there is any risk of damp penetration, then it would also be worth DPMing the bare wall with a tanking slurry first - cheap and easy to do. Then D&D your TLB straight on. That's as easy a job as can be, and the results will be amazing.

    If you then want to help the room be as cosy as possible, consider a finish like T&G timber cladding to dado height - or even full height behind the loo and basin as a feature. This can look great, and can even look contemporary or traditional depending on the finish given.

    Insulating the ceiling is also important, so it might be worth ripping down what's already there if you don't know there's insulation above it. Again, simply screw TLB straight on to the joists.

    The floor isn't as important - unless it's draughty - but still worth adding something there.

    Finally, ventilation is essential - so fit an extractor as you tear down the ceiling, unless you already have one on the wall?

    If you really want to go the battenroute, by all means do this instead.
  18. gingertimmins

    gingertimmins Member

    Thanks for the detailed reply. I'd kind of opted for the battening route as I assumed it would be cheaper. Am I right in thinking this?
    There's a hole in the wall ready and waiting for an extractor and the ceiling is definitely coming down.

    If I was to go for the thermal boarding option would I still go back to the brick?
  19. I think the D&Ding option must be cheaper. The only cost is TLB of the desired thickness and some adhesive, as opposed to battens, screws, insulation, and then plasterboard.

    And unless you also use TLB over the battens, then think about the level of insulation under that bare p'board - it'll be screwed directly on to timber battens which are peppered with metal screws.

    (If you are going 'battens', then ordinary plastic wall plugs are fine, but use corrosion proof screws - not sure which are best, but possibly those designed for exterior use such as on decking? For fixing p'board to battens, use proper p'board screws which are 'bugle'-headed and anti-corrosion treated.)

    For either option, you are best to go back to the bare wall for two reasons -- it'll gain you some space and it'll also ensure you aren't fixing over what could be existing loose plaster. An SDS drill with a large chisel bit should tackle this quite easily, tho' it would be noisy and unpleasant work - you DEF need ear defenders, a good dust mask and goggles. Chisel a V in to the surface until you reach the bare brick/block, and then hold the chisel at the required angle to cut along the surface and lift off the bonding plaster layer.

    Tbh, if you are certain that the existing surface is fully secure, then I don't see any reason (other than loss of room) why you couldn't just D&D over it all - use thin TLB so as not to lose too much room, even 35mm overall thickness stuff (25mm insul and 9.5mm board) will provide excellent insul value.
  20. If you really want to 'batten', then I'd go as Jord says above - use 2"x1" treated battens (eg - roofing battens) and screw them to the wall (either bare or existing depending on the level of work you plan to go to!). Since the 1" thickness of timber is then the effective insulation value achieved, I'd go for a simple and very cheap 'in-fill' of 1" Jablite insulation, which is effectively an expanded polystyrene foam (the white beady stuff). This will be dead easy to cut and squeeze in between the battens. Then over-board with the thinnest TLB you can get, which I think is around 35mm overall thickness.

    So we are talking about 2 1/4" overall thickness, but you will have the (to me) all important 'even' level of insulation provided by the TLB.

    Removing the existing plater and tiles would surely gain you about an inch, so you'd now only have lost an extra 1.25" space overall.

    If, however, you went for pure TLB D&Ded on, your 2" overall thickness would give you optimum insulation value.

    Nothing wrong with battening, but I would personally never entertain it unless it also had TLB over it all. I would never have bare p'board straight on to the timber battens because of all the metal securing screws going through in to the wall, and which are bound to provide lots of very cold spots immediately behind the bare p'board.

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